Mobile communications systems, such as cellular or personal communications services (PCS) systems, are made up of a plurality of cells. Each cell provides a radio communications center in which a mobile station establishes a call with another mobile station or wireline station connected to a public switched telephone network (PSTN). Each cell includes a radio base station, with each base station connected to a base station controller or mobile switching center that controls processing of calls between or among mobile stations or mobile stations and PSTN units.
Various wireless protocols exist for defining communications in a mobile network. One such protocol is a time-division multiple access (TDMA) protocol, such as the TIA/EIA-136 standard provided by the Telecommunications Industry Association (TIA). Another TDMA-based wireless communications technology is the Global System for Mobile (GSM) technology. According to TDMA, each radio frequency (RF) carrier carries a frame that is divided into plural time slots (or burst periods) to increase the number of mobile stations that can be supported per RF carrier.
Traditionally, wireless networks have been designed for carrying circuit-switched voice traffic. However, with the explosion of the Internet and intranets, packet-switched communications (e.g., web browsing, electronic mail, and so forth) have become common. As a result, packet-switched wireless technologies are being developed to transition to higher bandwidth and more efficient packet-switched communications of data as well as voice and other forms of real-time data over wireless networks.
Several packet-switched wireless technologies have been proposed to provide more efficient connections between a mobile station and a packet data network, such as an Internet Protocol (IP) network. One such technology is the General Packet Radio Service (GPRS) technology. One version of GPRS is adopted in GSM (Global System for Mobile) Release 1997. To provide further advanced features related to packet-switched communications, a later version of GPRS, referred to as Enhanced GPRS (EGPRS), is part of 3GPP (Third Generation Partnership Project) UMTS (Universal Mobile Telecommunication System) Release 1999 (also referred to as Release 3).
For even higher data rates, later versions of the 3GPP UMTS specification have been adopted. UMTS is based on the wideband code-division multiple access (W-CDMA) technology. In addition, an enhanced version of an Enhanced Data Rate for Global Evolution (EDGE) technology is referred to as the GSM/EDGE Radio Access Network (GERAN) technology.
Typically, in a wireless network capable of communicating packet-switched traffic, resources (e.g., a logical connection) are allocated to a mobile station only if there is actual data to transfer. Usually, it takes a relatively long time to allocate the resources to the mobile station. For example, in GPRS/EDGE (General Packet Radio Services/Enhanced Data Rate for Global Evolution) networks, the setup time for establishing a logical connection, referred to as a temporary block flow (TBF), can take several seconds on the uplink (from the mobile station to the radio network) and on the downlink (from the radio network to the mobile station). The demand for radio resources by multiple users (mobile stations) may exceed the amount of radio resources that are available. To enable another mobile station access to a radio network, the radio connection of a first mobile station that no longer has data to send is released, with the radio connection allocated to the other mobile station. If there is contention for radio resources among a large number of mobile stations, then overall performance for all mobile stations may suffer.